Brake-holder control mechanism



April 1952 G. A. GUERNSEY ET AL BRAKE HOLDER CONTROL MECHANISM 2SHEETS-SHEET 1 Filed Feb. 25, 1950 Y R W s m R m N m EE YR V S O muflfnP-H A w; G E

April 22, 1952 G. A. GUERNSEY ET AL I BRAKE HOLDER CONTROL MECHANISM 2SHEETS-SHEET 2 Filed Feb. 25, 1950 lNVENTOR 61 zwA. GuER VJEY A/YDXENNL'THA HARMON BY Ma a /.9

TTORN YS Patented Apr. 2 2 1952 BRAKE-HOLDER CONTROL MECHANISM Glen A.Guernsey, West Springfield, and Kenneth A. Harmon, Longmeadow, Mass,assignors to Wico Electric Company, West Springfield, Mass, acorporation of Massachusetts Application February 23, 1950, Serial No.145,692

13 Claims. 1

This invention relates generally to brake control mechanism for wheeledvehicles, The invention'is particularly useful in motor vehicles, of thetype in which the power of the motor is transmitted through a hydraulicclutch to the driving wheels of the vehicle, for the purpose of holdingthe brakes in'applied condition, after they have been applied by theusual means, thereby preventing the creeping of the vehicle, which wouldotherwise occur, after the vehicle has been brought to a stop and thebrake pedal has been released. The invention is also particularlyadapted for use with a motor vehicle having hydraulic brakes.

It has been heretofore proposed to use in a hydraulic brake system, forthe purpose described, a valve, which is interposed in the conduitbetween the master cylinder and the various brake cylinders and which isautomatically closed, when the speed of the vehicle or its wheels fallsbelow a predetermined value, in order to prevent return flow of thepressure fluid and thereby hold the brakes applied. The difficulty withthis prior art arrangement is that it operates, as described,invariably, irrespective of driving conditions. Thus, with the prior artarrangement, if the vehicle should be traveling on a slippery roadsurface when the brakes are applied, the wheels might be stopped withabnormal speed and the brakes become locked while the vehicle goes intoa skid, with the operator powerless to quickly re lease his brakes as hemay wish to do. The con trol of the brakes is taken away from theoperator at the very time when he needsto use the brakes most skillfullyto avoid skidding;

This invention has for its broad object the provision of a control forthe brake-holder, which is sensitive to the rate of, deceleration of thepropeller shaft of the vehicle, as distinguished from that of thevehicle itself, and which will render the brake-holder effective only ifthe rate of deceleration of such shaft is within normal limits,

whereby if the deceleration is faster than the normal rate, thebrake-holder will not become effective and the brakes cannot be locked,so that the operator is free to manipulate the brakes as he deemsnecessary. 7

The rates, referred to, areaverage rates over a very short period oftime. To state the matter another way, the controlling factor is thetime which it takes for the propeller shaft to decrease from onerelatively-low predetermined speed to another and still lowerpredetermined speed. If this decrease is effected too quickly, thebrakeholder will not be rendered operative, while if the decrease occursin a predetermined time or more, the brake-holder will be renderedoperative.

More particularly, the invention has for an object to provide atime-delay means, which is operable in a predetermined time after itsaction is initiated to render the brake-holder effective, together withmeans, to be driven by the propeller shaft of the vehicle and to bedirectly responsive to its speed, for initiating the action of thetime-delay means, when the speed of such shaft decreases to onepredetermined and rela-' tively-low value, and to stop the action of thetime-delay means and restore the latter to initial condition, when thespeed of such shaft decreases to a second and lower predetermined value.whereby if the decrease in propeller shaft speed occurs in less thansaid predetermined time, the action of the time-delay means is stoppedand it is prevented from rendering the brake-holder operative.

The propeller shaft-speed-responsive means and the time-delay means maytake various forms and several illustrative examples are shown in theaccompanying drawings in which- Fig. 1 is an elevational view of awheeled, motor-driven vehicle embodying the invention, such parts of thevehicle as are unnecessary to an understanding of the invention beingomittedf Fig. 2 is a sectional elevational view of anelectromagnetically operated, brake-holding rvalve, suitable for usewith the invention; and.

' Figs. 3, 4 and 5 are electrical diagrams-showing three examples ofcontrol systems for the brake-holding means.

' In Fig. 1, there has been indicated in diagrammatical form those partsof a motor-driven wheeled vehicle that need to be considered for anunderstanding of the present invention. There are shown the motor I; thecarburetor 2; throttle valve 3; an accelerator pedal 4, operable whendepressed to open the throttle valve 3 through suitable connections,such as rod 5, lever 6, rod 7 and lever B; a hydraulic clutch 9;transmission lo; propeller shaft H; wheels I2, the'rear ones of whichare driven from the shaft l I in the usual way; brake drums 13 on WheelsI2; brake shoes 14 in each drum; brake cylinders l5 one within each drumfor actuating the brake shoes by hydraulic pressure; a brake pedal I 6;master cylinder l1, having therein the usual piston (not shown)connected as by rod Hi to pedal l6 to be actuated by the latter, whendepressed, and transmit pressure through a conduit i9 to the severalbrake cylinders I5 and cause the brakes to be applied.

The brake-holder is indicated generally at in Fig. 1. It includes anormally open valve of any suitable kind adapted to be interposed in theconduit l9 between the master cylinder ll and the brake cylinders I5 andadapted, when closed, to preventreturn flow of the pressure fluid whichwould otherwise occur, when brake pedal I6 is released, and thereby holdthe brakes in applied condition. An illustrative example of one valveunit suitable for the purpose is shown in Fig. 2. The casing 2i hasslidably mounted therein a valve 2! for controlling the communicationbetween inlet and outlet passages 22'and 23 respectively connected onthe master cylinder side and brake cylinder side in the conduit [9.

The stem of valve 21 is in part a magnetic plunger 24 cooperating with asolenoid 25'. A spring 23 tends to hold the valve in open position. Thesolenoid 25, when energized, will close valve 25 against the pressure ofspring 28. Brake-holders I of this type, for the purpose described, areold and well known. They may be used to control brakes on all of thewheels or those on only some'of the wheels as is also old and well knownn 51. 9 1-,

The present invention has to do with the control of'the brake-holderand, particularly, with the automatic application of itnot invariablybut only'when driving conditions make it safe or desirable 510 to do.The control of the invention is operable to determine, when the brakesare applied, whether or not the propeller shaft (if the vehicle isdecelerating too rapidly. If it is, the brake-holder cannot be applied.If decelration is' not faster than ,a normal rate, the brakeholder willautomatically be rendered eiiec'tive just before the wheels stop. Thisresult can be accomplished in many ways. Examples are given herein ofseveral general ways of efiecting the result.

The first example is shown diagrammatically in Fig. 3 It involves atime-delay means and a propeller-shaftspeed-responsive means so relatedithatlthe decrease in speed of shaft 11 l, during 'application .of thebrakes by pedal 16, from l determined speed to another must occur after.thetiine-delay" means has become'operative. The time-delay meansasherein shown, is ajtime delay relay 21 having a' .coil.2 8, which whenenergized for some predetermined time interval, say for example a tenthof 'a 'second,'will maenetize core '28 'sufficiently to move switch 29against the force of a spring 29' into engagement with its contact 30and close an energizing circuit to selenoid 25. The time delay rela'y'isa standard commercial article available in the market. The delay iseffected in a usual and wellknown way by a closed ring 30' of copperwhich surrounds the pole face end of the core 28'. The aforesaidenergizing circuit may be supplied from the usual six volt storagebattery 3| of the motor vehicle. As shown, the energizing circuit forsolenoid zii is vas follows, from theungrounded tern al of battery 31,by wire 32,1the usual fuse 33;, wire 34, the usual ignition switch 35,wires 35,3! and 38, switch 29, contact 30, wire 39, solenoid 25, wire.4!], a closed switch 4! and wire .42 to groundand thus to the groundedterminal of battery 3!. Thus, when the relay pulls in andcloses'switchzli the solenoid 25 will be energized to close valve H andhold the brakes applied. The switch 4! is a release switch of anysuitable, kind, which can be opened at the will of the operator in orderto release the brake-holder. Conveniently, this switch may be opened bydepression of the accelerator pedal 4, as indicated in Fig. 1, beingclosed when such pedal is released and in engine-idling position andopen when such pedal is depressed and in all other positions. However,the particular form of the release switch is not essential to thepresent invention. The time-delay relay also includes a holding coil 33,which when energized, will magnetize core 28 sufficiently to hold switch2% closed, after it has been closed by the action of coil 28, but whichis incapable of itself of effecting the closing of this switch.

The pulling-in coil 28 and the holding coil 33 of the relay 27 arecontrolled by speed-responsive means, which as shown consists of amovable switch member 35 and fixed contact segments .55 and 45. Themovable member 34 is driven from the propeller shaft H. It is actuatedin the same way as the needle of a speedometer.

The contact segment 45 covers one speed range, for exampleonecorresponding to from 3 to 5 miles per hour of' the vehicle, when thelatter is driven by the wheels without slip. The segment 43 coversanother speed range nearer zero, say for example from 2 miles per hourto zero. The small numerals near the ends of these segments indicatesuch vehicle speeds. Contact is connected by a wire l? to one terminalof relay coil 28, the other terminal'of which is connected by a wire 43to wire 35. The outer end of member M wipes over the contact segments atthe stated, or other suitable speed ranges, and its inner end isgrounded. The energizing circuit for coil 23 may be traced as follows,from the ungrounded terminal of battery 3!, wire 32, fuse 33, wire 34,switch 3.5, wires 35 and 38, coil 28, wire it, se ment 45, member M tothe ground and thus to the grounded terminal of the battery. Thus, thecoil'ZS will be connected to the battery 3| during the period whilemember til is in engagement with segment 45]. The coil 28 is energizedto initiate the action of the time-delay means at a propeller shaftspeed corresponding to a vehicle speed of say 5 miles per hour. Theaction of the time-delay means will be stopped when memher 54 leavessegment 55 at a speed a little less than 2'miles per hour. If thedecrease from one 7 of these predeterminedspeeds to the other isaffected in a tenth of a second or more the relay willpull in and'switch29 will be closed to energize the solenoid 25 and apply thebrake-holder.

- If the decrease. in speed occurs in less than one tenth of a secondthe circuit'to coil 28 will be broken and the latter will becomedeenergized. Thus, the action of the time-delay means is stopped .anduch means is restored to its initial conditionbeiore switch .29 can beclosed. As the speed reachesZ miles per hour, the member M'engagessegment 46 and energizes the holding coil 43 of the relay. This coil hasone terminal cormecte d'by a wire 39 to contact 46 and its otherterminal is connected by ,a wire 50 to wire 3?. The energizing circuitfor coil 53 is as follows, fromlthje ungrounded terminal of battery 3!,wire 32, fuse 33, wire 34, switch 35, wires 36, 31 and 53, coil 43, wire4% segment es, member (14 to the ground and thus to the groundedterrninal of the battery. Thus, if switch 29 is closed, it will be heldclosed by coil 43 as long as mem-Z ber 44 engages contact 65. Release ofthe brake-' holder will occur by opening switch M, as for example, bydepressing the accelerator pedal 4. The circuit to solenoid 25 will bebroken and valve 2.! will be opened by spring 26., The switch 29,however, will not open until the shaft H turns fast enough to movemember 44 out of engagement with segment 46, in this case at a speed alittle above two miles per hour. Therefore, if the accelerator pedal 4has been depressed and the brake-holder has been released, the brakeholder can be reapplied simply by releasing the accelerator pedal andallowing switch 4| to close.

Another way of controlling the brake-holder is shown in Fig. 4. Here,three relays 5|, 52 and 53 are used. These relays have pulling-in coils54, 55 and 56 respectively mounted on cores 54', 55 and 56', which whensufiiciently magnetized pull switch members 51, 58 and 59 against theforce of springs 51', 58' and 59' into engagement with contacts 60. 6|and 62, respectively. Switch member 58, in addition, is adapted toengage a contact 63, when in its normal position, and to disengagetherefrom when coil 55 is energized. The cores of relays 5|, 52 and 53are provided with holding coils 64, 65 and 66, respectively. Eachholding coil, when energized, is not capable of itself of magnetizingits core sumciently to pull in the switch member of its relay but it iscapable of magnetizing such core suihciently to hold such member inpulled-in position, after it has been pulled in by the action of thepulling-in coil. The relays 5| and 52 are responsive to the speed of thepropeller shaft of the vehicle. C011 54 is so designed as to causeswitch member 51 to be pulled in at some predetermined and relativelylowpropeller shaft speed, which may for example correspond to a vehiclespeed of 5 miles per hour, and coil 55 is so designed as to cause switchmember 58 to be pulled in at another predetermined and still lowerpropeller shaft speed, which may for example correspond to a vehiclespeed of 2 miles per hour. Relay 53 is a time-delay relay, its coil 56functioning, after energization for some short predetermined timeinterval, say for example one tenth of a second, to magnetize its core56 suiiiciently to pull in switch 59. The pole face end of core 56 issurrounded by a copper ring 66' to effect the desired time delay.

The energizing circuit for the brake-holding solenoid 25 includesbattery 3|, wire 32, fuse 33, wire 34 and ignition switch 35, as before,and then extends as follows, wires 6'! and 68, switch 51, contact 66,wires 68' and 69, switch 58, contact 6|, wire 10, holding coil 65, wire10', switch 59, contact 62, wires 12 and 13, solenoid 25, wires 74 and75, release switch 4| and wire 76 to the ground and thus to the otherterminal of battery 3|. With the switch 58 positioned as shown a circuitto the brake-holder solenoid will be established on closure of switch51, as follows. battery 3| wire 32, fuse 33, wire 34, closed switch 35,contact 60, wires 67 and 6B, closed switch 51, wires 68 and 69, switch58, contact 63, wire H, coil 56, wires 18, i2 and I3, solenoid coil 25,wires 14 and i5 and closed release switch 4| to the ground and thus tothe other side of battery 3|. This last-named circuit, however, includesin series the relay coil 56 as well as the solenoid and the combinedresistances of these coils is so great that the current flowing in thecircuit is insufficient to cause coil 25 to close the brakeholding valve2|. The energizing circuit for coil 56 of the time-delay relay is thesame as the energizing circuit for solenoid 25 to and through switch 58and then extends as follows, contact 63, wire 11, coil 56, wires 18, I2and 13, solenoid 25, wires 14 and 15, release switch 4| and wire 16 tothe ground and thus to the other terminal of battery 3 I. The action ofthe time-delay means is initiated when the propeller shaft speeddecreases to one predetermined value, corresponding to a vehicle speedof say 5 miles per hour, when coil 54 draws switch 51 into engagementwith contact 60. This closes the described energizing circuit of coil 56of relay 53. This energizing circuit will be broken, when coil 55 ofrelay 52'- causes switch member 58 to engage contact.--

and disengage from contact 63. This occurs when the speed of shaftdecreases to a second and lower predetermined value, corresponding to avehicle speed of say 2 miles per hour. Thus, the action of thetime-delay means will be stopped and such means will be restored to itsinitial con-.

dition. If this occurs in less than the predetermined time intervalrequired for the time-delay relay 53 to close switch 59, thebrake-holdingv solenoid 25 will not be energized because coil 56:;- willbe deenergized by the pulling-in of switch 58,.

which in'leaving contact 63 breaks the energizing circuit to coil 56.Thus, although switch 58 en gages contact 6|, the energizing circuit ofsole-' noid 25 remains broken because switch 59 does... not engagecontact 62.

The relays must operate in the proper sequence. namely 5|, 53 and 52 inorder to energize solenoid 25.

one terminal of battery 3|, wire 32, fuse 33, wire 34, switch 35, wires61 and 68, switch 51, contact 60, wires 68, 69 and I9, coil 66, wires19' and 15, release switch 4| and wire 16 to the ground and thus to theother terminal of battery 3|.

The circuit to this holding coil 66 is closed when relay 5| pulls in atthe first predetermined speed."

Thus, as soon as the coil 56 of time-delay relay 53 closes switch 59,its holding coil 66 will be energized and available to hold this switchclosed.

Therefore, the breaking of the energizing circuit to coil 56 by theswitch 58 leaving contact 63.

when relay 52 pulls in, cannot affect switch 59.

which remains closed. Thus, as in the first example, if, when the brakesare applied, the speed of the propeller shaft decreases at a normalrate, the brake-holder will be automatically appliedbut if the decreasefrom the first to the second predetermined speed occurs in less than theselected predetermined time interval, then the brakeholder will not berendered effective.

The energization of the speed-responsive coils 54 and 55 of relays 5|and 52 is controlled-by,- a propeller-shaft-speed-responsive switch,which is or may be, of the same general nature as the breaker of theignition system of an automobile;

in back of the speedometer 64, which is connected to the drive shaft inthe usual mannerby a flexible shaft contained in a sheath 85;

Arm carries a contact 86 for cooperation'witli a stationary contact 81.The arm 80 is connected by a wire 88 to wire 67 and thus to the-un- Ifoperated in the sequence 5|, 52 and 53, the solenoid 25 will not beenergized, as has just been described. Assuming that relay 53 pulls in,before relay 52 it will cause switch 59 to engage. contact 62 and theholding coil 66 will then hold. this switch closed. The energizingcircuit for holding coil 66 may be traced as follows,,from-.

7 grounded terminal :of battery 93!. contact 81 sisconnected by wires'89 and all-to one'ter urinal o f coil i. 'I'he other terminal of thelatte :isoonnected by wires Ial and 92 to wire 1:5 :and through thelatter, release switch 4| and wire 1.16 to the ground and the otherterminal of battery 31. A iwi're '93 connects wire 89 to one terminal of-'coll 55 of relay 52 and the other terminal of this coillissconnecte'dby a "wire 9 1 to wire 13am :thus through solenoid 25, wires T4 sand 1'5release :switch El, and "wire 16 to'the g'r'ou d'hnd thus to theoth'e'rterminal of battery 3L eholdi ngcoil fifi of :rela'y 51 has onetermlnal connected to wire 68' and thus to contact 60 and the otherterminal connected by a wire 951cc wire 92 and :thus through wire it,release switch 1H,, and "wire '16 to the ground and battery While theenergizing circuit of coil as .is closed by the closing of switch 5] theenergizing. circuitsof=coils154 and :55 are :closed by thespeedresponsive switch only for the short time fin terval during whichthe contacts as and '8] are engaged. This vtime varies with thepropeller shaft speed, decreasing as such speed increases;

. 54 is subsequently broken by the speed-responsive switch; Similarly,the inductance of coil 55 and the solenoid 25, with which it is inseries, is such that enough current will be passed through the coil 55'to magen'ti'ze core 55' suficiently to pull in switch 58 only when thepropeller shaft speed is at its lower predetermined value, correspondingto a vehicle speed of say 2 miles per hour; While coil 5515 connected inseries with the brake-holding solenoid 25, it is to be noted that coil55 is of such high resistance that, when 7 its energizing circuit isclosed, there will not be enough current flow through solenoid to enableit to close the brake-holding valve 2 l.

The operation of the Fig. 4 form of the invcntion', will now bedescribed. Assuming that the: vehicle is in motion and the operatordesires to stop it, he releases accelerator 4,, thereby causing switch4| to close and presses down on the brake pedal 85 which applies the,service brakes. As the speed of the propeller shaft decreases to thefirst predetermined value, the re-'- lay 51 will pull in and move switch51 into engagement with contact 66. Thiscloses the on ergizing circuitfor holding coil 64, which therefore maintains switch 5'! closed untileither the release switch 4| or the ignition switch is opened. Theclosing of switch 57 also closes the energizing circuits for the holdingcoil 65 and coll 56 of the time-delay relay 53. The .leuuier' will, inthe selected predetermined time, say for example one tenth of a second,closeswitch 59. If the propeller shaft speed does not decrease to thesecond and lower prede tcrmined value until the predetermined time haselapsed, switch 59 will have closed and the subsequent pulling-in ofswitch 53 by relay'52 will 7 0011 56 'of the time-delay relay will "bebroken and switch 59 cannot "close. Therefore. the engagement of switch58 and contact 51 by the pullin'g in of relay '52 cannot close theenergizing V circuit to 'sol'enoid 25 so that'the brake=holder isinoperative.

Release ofthe brake hol'de'r is efiected by opening the release switch4!, as by depressing the accelerator pedal 4. This will open theenergizin'g, circuit to solenoid 25 and-also the energiz ing icircuitsfor all the relay coils 54-, 55, 56 and all the holding coils -64, '65and 66 so that the switches 57, 58 and 59 will ope'nand the parts willbe restored to their initial positions shown. ready 'for'subsequentoperation in the manner described.

Another "example of the invention is shown in Fig. 5-. lhre'e relays 96,53-1 and 98 are utilized. Relay 96 includes a coil 99, which is mountedon a magnetiz'abl core I69, and. a switch I'M. whichis normally heldopenby a spring I02 and which is "movable :by magnetic attraction of coreI60, when the coil is sufficiently energized, into engagement with acontact 103-. Coil 99 will be thus energized at a propeller shaft speedcorresponding. to a vehicle speed of say five miles per hour in a mannerlater to be described. Re lay 9-! includes a coil EM, which. is mountedon a niagnetizable core 105, and a switch 106,

' i, which is normally held engaged with a contact i9? by a spring I63and which is movable by the magnetic" attraction of core H15,- when coilHi l is sufficiently energized, into engagement with a contact H39. 0011I94 will be thus en'- ergiz'ed at a propeller shaft speed correspond=ing to a vehicle speed of say two miles per hour, as will later appear.Relay 93 is of a time-delay relay. It includes a coil llll, whichismounted on a magnetizable core I l I having a copper ring Hisurrounding its upper or pole face end, and a switch member H2, which isnormally held open by a spring H3 and which -is movable by magneticattraction or core Ill into engagement with a contact Il l after itscoil H0 has been energized for some predetermined short time; whchmayfor example be one tenth of a sec on The energizing circuit for coil lllwill, as be= fore, include the battery 3!, wire 32,- fu'se' 33, Wire 34,and ignition switch 35, and it then extends by wires H5 and H6, switchI96, contact I07, wire H7, coil H0, wire H8 c0n'tac'tl03 and switch leito the ground and thus to the other and grounded terminal of battery 3!;This ehergizing circuit will be closed when relay 96 causes'switch llllto engage contact I03} which occurs at the first nained propeller shaftspeed. This circuit for coil H0 will be changed when relay 9'! operatesat the second-namedpredetr mined speed of the propeller shaft to moveswitch I86 out of engagement with contact I01 andinto engagementwithcontact- I99. for coil H0 is not physically broken but a resistor l 19,which is connected across betweenwiis I I6 and Ill and is'nornial-ly'shunted out by switch i96 when engaged with contact Hi1,- will b in:-

troduced into the circuit-to out down the'curr'e'nt flow to-the'magnetcoil I I0. This change reduces the current flow through magnet coil H0to an extent such that it is unable 'to pull in switch H2 although itis" able, if the Switchhas" been previously closed, to hold the switchclosed. The coil H9 is thus converted from a pulling-in coil to aholding coil. The circuit to the pulling-in betcr e relay 53, then theenergizing circuit to" 1 coil: is'disable'd as effectively by theintroduction- 9 of resistor II9 into its circuit asv if a physical breakin the circuit occurred. The arrangement is the equivalent of the relay53 of Fig. 4, where separate pulling-in and holding coils are used andthe holding coil remains energized after the pulling in coil isdeenergized.

The movement of switch II2 into engagement with contact IE4, followed bythe movement of switch I into engagement with contact I09 closes anenergizing circuit to the brake-holding by wire I22, closed releaseswitch M, and a wire of battery 3I. If, however, the relay 9'! causesits switch I06 to engage contact I09 before relay 98 has had time toclose switch H2, then the brake-holder cannot be rendered operativebecause the reduced current flow through coil III? is not sufficient toclose switch H2.

The propeller-shaft-speed-responsive means for controlling the relays 90and 91 includes a minal of coil I04 and the other terminal of coil 03 isgrounded. The other terminals of choke coil sections I24 and I25 arerespectively connected by wires I30 and I3I to spring contact fingersI32 and I33. These fingers are alternately en- "gaged by one end of apivoted switch arm I34, 'the other end of which is connected'by a wireI35 to wire H and thus to the ungrounded side of battery 3!. The switchI34 is drawn by a spring I33 into engagement with a cam I31, which isdriven by the propeller shaft II as for example by means of thedescribed speedometer shaft 82. As shown, this cam has six lobes andthus the arm I34 will be oscillated six times during each revolution ofshaft 82. This switch arm is arranged to move into engagement with andthen, by continued movement, flex each spring contact finger. It is alsoarranged to engage one spring contact finger before it disengages fromthe other. Thus, the finger I33,

which as illustrated has been previously. flexed downwardly, will moveupwardly, as switch arm I34 swings u wardly, until the latter engagesfinger I32. On continued u ward movement, arm I30 will disengage fromfinger I33 and then flex finger I32 upwardly. The arrangement is:

such that one finger or the other is always connected to the arm I34.Thus, one section I24 or the other section I of the choke coil is alwaysconnected to the battery (when ignition switch 35 is closed) t rough acircuit which includes the relay coils 99 and I04 arranged in parallel.One such circuit is as follows, from the ungrounded terminal of battery3I, wire 32, fuse 33, wire 34, closed switch 35, wires H5 and 535,switch arm I34, finger I32, wire I30, choke,

09 to the ground.

.When the circuit is closed to onesection of the choke coil, a currentflow is established but,

was

.10 solenoid 25. This'energizing circuit is the same 'as that for magnetcoil H0 to switch I06 and then extends by contact I09, wire I20, switchI I2, contact I I4, wire I2I to solenoid 25 and thence I23 to the groundand thus to the other terminal and close switch I I2. This may, forexample, take due to the inductance of the coil, there is a lag inbuilding up the current and time is required for the current to reachits maximum value. As the speed of the cam increases, the time intervalduring which a circuit to either section of the choke coil is closed,decreases and the maximum values to which the current can be built updecrease. A current flow is built up through one section of the chokecoil in one direction and then through the other sectionin the otherdirection and an alternating current Wave is produced. This wave issmoothed out to some extent by the use of a condenser I 30, one side ofwhich is connected by wires I39 and I21 to the mid-point of the chokecoil, and the other side of which is connected through a resistor I 40to the ground. The choke coil and the circuit breaker I32, I33 and I34form a current-limiting means and they limit the current flow throughboth relay coils 99 and I04 proportionately'to the speed of thepropeller shaft of the vehicle, the current decreasing as the shaftspeed increases. In this particular example, the coils 99 and I04 havesubstantially the same resistance and the same number of turns and thecurrent flow though each is the same. While the magnetic pull of bothrelays is the same, the speed at which the two relays pull in to closetheir respective switches is made different by adjustment of the tensionof springs I02 and I08 acting on the switch-carrying armatures of therelays and/or the air gaps between such armatures and their respectivecores. The relay 93 will pull in when the propeller shaft I I reachesthe higher of the two predetermined speeds but therelay 91 will not pullin until a greater current flow has been produced to overcome thegreater resistance to movement of its armature and this occurs only whenthe propeller shaft decreases to the lower of the two predeterminedspeeds.

It is desirable, in order to avoid arcing between the contacts on armI34 and those on spring fingers I32 and I33, to bridge across eachcooperating pair of such contacts a condenser, such as shown at MI andI42.

In the diagram of Fig.5, the coils 99, I04 an I I0 have resistances of12.68, 12.19 and 12.17 ohms, respectively: the choke coil sections I24and I25 each have a resistance of 2.49 ohms; the resistors I I9 and I40are of 17.8 and 3 ohms resistance, respectively; the condenser I38 is of1000 mid. capacity; and the condensers MI and I42 are of .1 mid.capacity. These values are not critical but they will serve asillustrative examples of values found suitable for the purposedescribed. The relays are of standard form and can be procured from anyrelay manufacturer who will design them to function under the conditionsstated.

In the operation of the Fig. 5 form of the invention, assuming that theignition switch 35 and release switch 4| are closed and that theoperator has depressed the brake pedal to apply the brakes, as thepropeller shaft of the vehicle slows down to the first predeterminedspeed, relay 93 will pull in and close switch I03. This will close theenergizing circuit to coil I '0 and initiate the action of thetime-delay relay 93. If the propeller shaft decelerates at asufficientlylow rate, the coil III), which has high inductance, will have time tobuild up sufiicient flux in its core, III to pull in one-tenth of asecond. The closing of switch 2 prepares the energizing circuit forsolenoid 25 so that it will be closed, when thelow speed relay 9! pullsin and moves switch I 06 from con tact.,.l0l:=to contactlllfi.Thesolenoid'fidwill be energized tozclose .valve .21., and the resistorH9 will berplaced L, in... circuit. with. coil... I Hi, reducin the.current .fiow therethrough-to.that.necessary to relay- 911 will.- pullin, before-the time-delay relay 9,8..has. had; time..-to build. up.enough fluxin core lfll l ytocauselswitch llzt'oclose, This causes. theresistor l l 9atoloe. placedin. series withcoil no to limita-the-maximum.cnrrentthat canzhe built up -i1l"1th6.-60i1 to a value too low tov beable. to pull Accordingly, the, energizing the switch l.l2 circuitzoiythe solenoid. Ziremains open-and the brake-holder.- will notbe renderedoperative.

Thai-Fla e -form.-,o1 theinvention has the. advantagethatan accidentalopening ofthe. release switch l-lcwill not. compelcomplete recycling ofthe control in; order to render the brake-holder operativezagain... E01.example, if the operator accidentally depresses thev accelerator pedaland opens switchs lil, whereby the brake-holder -is released. the lattercan be re-appliedhy releasing thoaacce'lerator. pedal-beforethe vehicleacquires any; snbstantial-.= speed. The circuit to coil I ill willnot-be broken until .the propeller shaft of the vehlelezturnsatairspeed, corresponding to a vehicle: speed of substantially more thanfivemiles an hour; The release speeds of the .relays. stand 1-04 are, ofcourse, greater. than the. pulling-in sneedss. The-edropping out ofrelay lEM-will cause an-.,increase-in current through coil' I Ill andrelay 98eremains. energized, to hold switch H2 closed.

ltaisethejdropping; out; or, relay. 96 which. breaks theaenergizlngcircuit-to coil. I So and-releases. the brake-holder Thus, if thereleaseswitch at ,having been openedfls: closed before; the propellersha-Itispeed-exceeds therelease speedof relay 9%,

they-energizing;circuit to solenoid 25 can he. reestablishedto apply;the brake-holder.

Thespeeds, referred to herein, are. illustrative examples. They may bevaried through substantialllimits' as. desired by changing thecharacteristics-pf the-relays, choke. coil and breaker switchl Also the.release speed of the relays. may bezreduced by reducing. the. current.flow therethrough-when. therelay is; pulled in inmuch the VwilLcause-the brake-holder to. be rendered efiectivein a: predetermined.time. If oncontinuecl decelerationpf. the; shaft, the second and lowerpredeterminedispeed is reached in less than said timythebrakeeholdercannot be rendered operative; Ifhis'. featureprevents the brake-holderfrom lockingthe brakes. in applied condition, when the wheels ofjthe,vehicle are on slippery surfaces and'stop suddenly when the brakes areapplied;

The operator is left-free toreleasehis brakes if .heldeems it necessary.If it t'akesthe same or moregthan said predetermined time for thepropeller shaftto' decreasefromthehigh tothe' low predetermined speed,the brake-holder willbe operative. .Thus, the control decides Whether ornot'it'is'safe for the brake-holder to be used and 12. renders the sameoperative: or-inoperative cordingly,

What is claimed is:

3;. Brake control mechanism iorwheele'd; vehicies, comprising, abrake-holder;formaintaim ing the brakes. in applied condition after theyhave been applied, means lcr autornaticallyactuating the brake-holderincluding a timing means. 0; erahlein a predetermined time. after itsaction isinitiated to render the brake-holder. operative, and first andsecond speed-responsive controls including anactuating member adaptedforconnection to and to he actuated by the, propeller shaft of thevehiolefor respectively starting the timing means at onerelatively-lowpredetermined speed andlcr disabling itat another and lowerpredetermined" speed, whereby if. the decrease frornnthe first to thsecondjspeedjoccurs inless than, said. predetermined time the brakeholder loin-operative. V

2; Brake control mechanismjior wheeled vehicles, comprising,a.brakerholder.forholding the brakes in, applied condition, aftertheyhave. been applied, a time-responsive controlwoperableina predeterminedtime after its action is initiated to render said brake-holderoperative, afirst speedresponsive controlincluding an actuating memberadapted forconnectionto andto. be actuated by and .be directlyresponsive to. thespeed oithe propeller shaft of the. vehicle forinitiatingthe actionof. the time-responsive control when the speed of.such shaft, decreases to a first. predetermined value, a secondspeederesponsivecontrol actuatedby said actuating member and. adaptedto. disahl'e;saidtimerresponsive control, when the speed or.said...shaf.t.decreases to. a. second predetermined value, whereby ifthe. speed changeiro-m said'first to said secondvalue occurs in more orless than said predetermined time the brake holder: will. respectivelyhe.-rendered-..operative or inoperative, and a. releaseifor releasing.the. brake- V holder; at the will of. the operator;

3. Brake control mechanism. for wheeled, ve-

hicles comprising, .a.- brake-holder. for: holdingthe c brakes inappliedcondition after theyhaye been applied, and. controlling, meansfor thebrakeholder. comprising. first, second and. third, controlswhich, Whensuccessively rendered operative. in a predetermined sequence,render the brake-holder efiective, actuating. means. for the first. and.second controls adaptedfor connection to andtohe. driven by the,propeller. shaft ofthe vehicle and directly. responsive to the speedthereof, said first control adapted. to be rendered operative whenthespeed of such shaltdecreases to one relatively-low,predeterminedvalue, said secondcontrol adapted to be rendered oper ative. when thespeed of suchshaftdecreasestoa second and lower predetermined value; anda third control responsive to time-and initiated'by the first control,;when the latter is rendered operative, and rendered operatiye-v apredetermined short time interval afteritsfinitiation, saidcon. trollingmeans being operable to rendenthebrakeholder effective when the, first,third and second controls are successively rendered: operative in the,order statedand inoperative when the first, second and third. controls:are: successively. rendered operative in the lastenamedsequence; andmeans for releasing the brake-holder;operable-at the will o-f'theoperator ofqthe vehicle.v V

4. Brake control mecnanism for wheeledvehicles, comprising, abrake-holder; electrical means for actuating the brake-holder, an.enersizing: circuit for said means. a.;normally..-open 13 switch in saidcircuit, a magnet coil operable when energized for a predetermined timeto close said switch, an energizing circuit for said magnet coil.

said switch, an energizing circuit for said magnet coil, andspeed-responsive switch means including an actuating member adapted forconnection to and to be actuated by the propeller shaft of the vehicleand located in said last-named circuit for closing the latter at onepredetermined and relatively-low speed and for disabling it at anotherpredetermined and still lower speed,

whereby if the change from the first to the sec-' holding the brakes inapplied condition after they have been applied, an energizing circuitfor said electromagnetic means including a time switch 5,

operable to close in a predetermined time after its action is initiated;electrical means for controlling the action of the time switch andincluding an electrical circuit, first and second speed-responsiveswitches and an actuating member therefor adapted for connection to andto be actuated by the propeller shaft of the vehicle, said firstspeed-responsive switch operable to close such circuit at a firstpredetermined low speed, said second speed-responsive switch operable todisable such circuit at another and lower predetermined speed; wherebysaid electromagnetic means will be energized only if the decrease fromthe first to the second named speed occurs in said predetermined time orin a longer time.

'7. Brake control mechanism for wheeled vehicles, comprising,electromagnetic means for holding the brakes in applied condition afterthey have been applied, and controlling means for said electromagneticmeans, comprising, an energizing circuit for said electromagnetic meansincluding a time switch operable to close in a predetermined time afterits action in initiated, and normally-open first and secondspeed-responsive switches, actuating means for said lastnamed switchesadapted for connection to and to be actuated by the propeller shaft ofthe vehicle and operable to respectively close the first and secondspeed-responsive switches when the speed of such shaft respectivelydecreases to a first predetermined low value and a second and lowervalue, electrical means for initiating the action of said time switchand comprising an energizing circuit including said firstspeedresponsive switch, and a third and normally closed speed-responsiveswitch by said actuating means and opening when the speed decreases tothe second-named value.

8. Brake control mechanism for wheeled vehicles, comprising, abrake-holder for holding the "1'4 brakes in applied condition aftertheyhavebeen applied, a time responsive control for actuating saidbrake-holder in a predetermined time after its action is initiated;electrical means for controlling the time responsive control includingan electrical circuit, a normally open first switch and a normallyclosed second switch in such circuit;

first and second electromagnets forrespectively' closing and opening.the first and second switches. energizing circuits for saidelectromagnets, and

a circuit breaker in the last-named circuits in-i eluding an actuatingmember adapted for con nection to and to be driven by the propellershaft of the vehicle and in direct response to the speed thereof foropening and closing the last-named circuits at a rate proportionaLto thespeed of said shaft, said first electromagnet having characteristicssuchas to be energized sufficientlyfto close the first switch at andbelow a first and relatively low speed of said shaft, the secondeletromagnet having characteristics such as to open the second switch ator below a second and lower predetermined speed of said shaft.

9. Brake control mechanism for wheeled vehicles, comprising,electromagnetic means for holding the brakes in applied condition afterthey have been applied; an energizing circuit for said means; atime-delay relay having a switch located in said circuit, a first coiloperable, when energized for a predetermined time, to close said switch,and a second coil operable, when energized, to hold said switch closedafter "it has been closed by the first coil but incapable of itself ofclosing said switch; an energizing circuit for said first coil andspeed-responsive control means therefor, including an actuating memberadapted for connection to and to be actuated by the propeller shaft ofthe vehicle and operable to close said second circuit, when the speed ofsuch shaft decreases to a first and relatively-low predetermined valueand to open said second circuit when the speed of such shaft decreasesto a second and lower predetermined value; whereby if the change fromthe first to the second predetermined speed is' effected in more or lessthan said predetermined time said switch respectively will or will notbe closed by the first coil of said relay, an energizing circuit forsaid holding coil, control means for the lastnamed circuit operable toclose the same not later than when said switch closes, and a releaseswitch in the first energizing circuit normally closed when the brakesare applied and adapted to be opened by the operator of the vehicle todeenergize said electromagnetic means and release the brakes.

10. Brake control mechanism for wheeled vehicles, comprisingelectromagnetic means for holding the brakes in applied condition afterthey have been applied, an energizing circuit for said means including aswitch; a time-delay relay for actuating said switch and including afirst coil operable, when energized for a predetermined time to closesaid switch and a second coil operable, when energized, to hold saidswitch closed after it has been closed by the first coil but incapableof itself of closing said switch; an energizing circuit for said firstcoil, first and second speed-responsive switches, and an actuatingmember for the two last-named switches adapted for connection to and tobe actuated by the propeller shaft of the vehicle and operable toactuate the first speed-responsive switch to close said second circuitat a first relatively-low predetermined speed of said shaft, andoperable to; actllfifiek-thfi second. speed-responsive. switch to organ.said: second circuit. ata. second and.v lower predetermined speed.ofsaid shaft, whereby if the, change fromtheflrsttov the secondpredetermined speed iseiiected inmore or less. than said predeterminedtimeesaid first switch respectiveliywill or, will, not be closed-by thefirstcoil oi" said relay, an energizing circuit for said holding: coil,and. a releaseswitch in thefirst energizing. circuitnormally closedwhen. the brakes-mare applied. and adapted'to, besopened by the,operator oi. the, vehicle to deenergize said electromagnetic means andrelease the. brakes.

lihBrake control. mechanismior wheeled ve' hioles. comprising,electromagnetic means for holding, the brakes in applied. conditionafter they.v havelbeenappliedan energizing circuit for .said; meansincluding aswitch; a. time-delay relay for. actuating saidswitchandincluding a first coil, operable,,whenenergized, for a predetcrminedtime, to close said switch, and-a second coiloperable, whenenergized, tohold said switch closed after it has been, closed by the first coil butincapable of itself. of closing said. switch; an

energizing circuit, for said first coil, speed-re- .whereby, if? the.change from. the first. to the second predetermined. speed is effected.in more or less than saidpredetermined time the secondswitchirespectively. will. or, will not .be closed. by the first coil ofsaid. relay, anenergizing circuit for. said-holding coil, control means;for. closing said last-named circuit ,notlater. than when saidfirstswitchclcses, and. a. release switch in the first. energizing,circuit. normally closed when the brakes are appliediand adapted tobeopened by the operator of; the. vehicle todeenergize saidelectromagnetic means and release the brakes.

12, Brake. control mechanismfor wheeled. vehicles, comprising,electromagnetic. means for holding thev brakes in applied condition.after, they have. been applied. an energizing circuit .for

said. means; a timeed'elay relay includingv a switch, located, in. said.circuit, a.- first. coil. operable. when. energized. tor. a,predetermined time to close .said switch, and a..se,cond .coil' operablewhen energized to hold said switchclcsed f after it has been closedbyvthe..firs.t coilbut. incapable of itself. of closing said switch; anenergizing cir- "cuit'for saidlfi'rst coil,,.second, and. thirdswitches.

included in series. in said second circuit, firstand secondelectromagnets adapted when. energized to respectively closethe. second.switch and. open the third switch, third. and fourth.energizinggcircults for theelectromagnets of the. secondand thirdswitchesa circuitbreaker in thethirdand fourth. circuits and. includingan. actuating member adapted for connection. to. and to be actuatedby'the propeller shaftof the vehiole, wherebythe thirdandliourth.circuitsv are closed and opened at a. rate proportional tothe. speed of r said shaft, said firstelectromagnetbeing energizedsufficiently, to. close the. second switch at one predetermined andrelatively low shaft. speed and. said secondelectromagnet beingenergized sufficiently to openthe, third switch at another and. lower.predetermined shaft speed, an energizing circuit for. said holdingcoil,control means for. closing the last-named circuitnot. later thanwhen. said. first. switch. closes, and. a release switchin the firstenergizing circuit. normally closedwhen the brakesare applied, andadapted to be opened by the. operator of. the vehicle to deenergize saidelectromagnetic means and release the. brakes.

13. Brake control means for wheeledvehicles, comprising, a brake-holder,electric means for actuating the brake-holder, an energizing'circuit forsaid means adapted for connection to a source of electricity, a switchin said circuit, a second electrical nieans for actuating said switch, asecond energizing circuit for said second means adapted for connectionto said source, and means for varying the voltage applied from saidsource to the second energizing circuit inversely with the speed of thepropeller shaft of the vehicle, said last-named means comprising twochoke coils connected together atone, end and to. one point in saidsecond circuit, switch means including two contacts. which are.connected'one to each of the otherends of the choke coils, a movablemember. which is connected to said second circuit at another point, andactuating means adapted for driving connection with the propeller'shaftof the vehicle for moving said member to engage alternately with saidcontacts and engage With one beforeit disengages from the other. V

GLEN A. GUERNSEY.

KENNETH A. HARMON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

